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From Geoffrey Young <>
Subject Re: Trying to get a backtrace while debugging stacked handlers bug
Date Tue, 20 Feb 2007 13:46:43 GMT
Fred Moyer wrote:
> Hello,
> I've been hacking on this issue here -
> and am trying cause a core dump so I can look through the backtrace with
> gdb and figure out what's going on. 

core dumps on purpose - excellent!

have you tried gdb or ddd?  A::T supports the most execellent -d option

  $ t/TEST -dddd -v t/apache/foo.t

will launch ddd and stop at an automatic breakpoint just after the child
process is spawned (iirc).  there are also ways of setting your own
breakpoints through -breakpoint= and even some fancy .file, but I forget
what it's called.

> I'm a bit new to this level of
> debugging so please bear with my naivete (have had my copy of practical
> mod_perl handy so that's been my guide but I still need a little help)
> To do this, I pushed a handler which should core dump, as so:

>     Debug::DumpCore::segv();

I've never used this before, so I have no idea :)

>  }
> but I'm not getting a core file.  I've built mod_perl with MP_TRACE=1
> and MP_DEBUG=1, and set MP_PERL_TRACE=all,

make sure you've also built with MP_MAINTAINER=1, for which I think
you'll also need to have compiled httpd in maintainer mode.

> but I haven't gotten the
> granularity I desire when running the test with
> ./t/TEST -VERBOSE t/hooks/stacked_handlers2.t.  I get the call stack
> down to the handler level, but I need to get a more fine grained view of
> what functions are being called.

I'm not very good with the debugger, but this might help you

I prefer ddd over gdb for this kind of walkthrough, mostly because I
don't know the gdb commands.  but t/TEST -d will accept either gdb or ddd.

> Any advice welcome :)   I know I'll figure it out eventually, but I'm
> guessing that this stuff is old hat to everyone on this list.


have fun :)


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